The present invention relates to an apparatus for supplying gravure coating material, and more particular to an apparatus for supplying gravure coating material in which a fixed quantity of coating material can be supplied to a gravure roll and coating material can be uniformly coated onto a running substrate.
According to a conventional gravure coating device, a lower portion of a gravure roll is soaked in coating material accommodated in a pan-shaped coating material reservoir having an open upper side, and then the gravure roll is rotated, thereby supplying coating material to cells (engraved portions) formed on the outer periphery of the gravure roll and rolling up the coating material. In the meantime, surplus coating material is scraped off from the outer periphery of the gravure roll by a doctor blade, a fixed quantity of coating material filled in the cells (engraved portions) is supplied to a contacting portion of a continuous substrate such as a thin film or a web and the gravure roll, thereafter the coating material is transferred to the substrate and coating is performed.
However, in the conventional gravure coating device, since coating material is supplied to the coating material reservoir more than coating material is coated on the continuous substrate by the gravure roll, coating material always overflows the coating material reservoir. Therefore, it is necessary to install a mechanism for collecting overflowed coating material and recirculating the same, and it is troublesome to clean the mechanism and the pan-shaped coating material reservoir when replacing the gravure roll.
Further, since coating material is recirculated, it is oxidized or deteriorated by absorbing water during recirculation. As a result, the color of recirculated coating material is different from that of coating material already coated, thereby causing uneven coloration of coated portions. Furthermore, minute bubbles are mixed in coating material during recirculation, thus causing poor coating.
In another aspect, according to the conventional gravure coating device, it is difficult to roll up coating material having high viscosity such as magnetic ink by the gravure roll. Particularly, when rotating the gravure roll at high speed in order to perform high speed coating, coating material is not filled in the cells (engraved portions) formed on the outer periphery of the gravure roll, whereby coating cannot be performed frequently.
In order to eliminate such drawbacks, there has been another type of gravure coating device in which coating material is directly supplied into the cells (engraved portions) of the outer periphery of the gravure roll by a nozzle, and then surplus coating material is scraped off by the doctor blade.
However, since supply of coating material from the nozzle is limited to a small quantity, coating speed is limited to extremely low speed. Further, since coating material scraped off by the doctor blade is recirculated, this type of gravure coating device using the nozzle still has the same drawbacks as the former type of device mentioned above.